The Recruiting team at AW Computing captures the job acceptance and date of hire of...

The validation rule must fire when two things are true:

Job_Accepted__c is already populated

Hire_Date__c is being changed

Salesforce’s ISCHANGED() function returns true when a field’s value changes from its previous value, and formula functions can be used in validation rules.

So this formula prevents users from changing the hire date after the candidate has accepted the offer:

NOT(ISBLANK(Job_Accepted__c)) & & ISCHANGED(Hire_Date__c)

Why others are incorrect:

The other options either use the wrong logical operator or validate the opposite condition. A validation rule must return TRUE only when Salesforce should block the save.

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